Use MT-32. Either a real one or an emulator. ScummVM comes with an MT-32 emulator. You need the MT-32 ROMs, though.
This requirement won't change in the final version, either.

You might also try ScummVM's ability to translate the MIDI to GM. Depending on your wavetable, this can sound rather good too.

but since the audio is on the se version, surely that's not using mt-32 otherwise it wouldn't be playing, so it must be just the music converted into some other audio format much like the cd audio version of MI1 was?